Note use-by date then start to explode (8)
I believe the answer is:
detonate
'to explode' is the definition.
('detonate' can be a synonym of 'explode')
'note use-by date then start' is the wordplay.
'use' is an anagram indicator (I've seen 'used' mean this).
'by' means one lot of letters go next to another.
'date' becomes 'd' (abbreviation e.g. dob - date of birth).
'then' means one lot of letters go next to another.
'start' becomes 'ate' (I can't explain this - if you can you should give a lot more credence to this answer).
'note' is an anagram of 'eton'.
'eton' after 'd' is 'deton'.
'deton'+'ate'='DETONATE'
Can you help me to learn more?
(Other definitions for detonate that I've seen before include "Cause to explode" , "Set off explosive device" , "Start 15 [EXPLOSION]" , "let off" , "go off with a bang" .)